27 A New Method for Valve Seat without Ring 2002-32-1796

A surface modification method by electrical discharge has been developed for the valve seats of aluminum cylinder heads. This method employs a conventional electrical discharge machine to generate continuous discharge arcs between an electrode and a cylinder head, whereby the molten electrode material is transferred and clad onto the valve seat area on the cylinder head. Using this new cladding method, a wear-resistant cladding can be formed on each valve seat area in a matter of minutes and, if the same number of electrodes as valve seat areas are set one on one, all the valve seat areas can be clad simultaneously. The advantages of this method include local cladding capability, outstanding adhesion, quick cladding speed, and excellent adaptability to various types of engines. The chemical composition of the cladding was determined by a preliminary test using dynamo engines, and the durability of the cladding was evaluated using the same dynamo engines. The results indicate the applicability of the surface modification method to high-output engines. This paper reports on the procedures and test results of this discharge cladding method.